Help! Huge iMovie project won't export properly

I've been working on a auto racing DVD in iMovie for about two months now. It is about 1 hour 20 minutes long with each clip ranging from 5 to 20 seconds. I used multiple transitions and titles, as long as background music.

The problem:

I exported the movie in HD. It took about 8 hours to export. (Seems normal for a hour+ project). The first 10 minutes seem to play perfect but after that the audio doesn't match up with the video and it starts to get all screwed up.

Any ideas on how to fix this and make my computer export it properly so the entire video will play clean/correctly?

Also, I do have Final Cut Pro, but I am not skilled in that program yet so I didn't use it. I tried to export it into Final Cut because I figured it has a lot of different ways to export the video, but it said it wouldn't be compatible with the same transitions or custom titles from iMovie that are in my project...

If you are going to edit anything longer than twenty minutes, consumer video-editing software isn't going to get you anywhere. iMovie is not a heavy-duty editing program, and it doesn't claim to be. If you add too many transitions, audio tracks, video clips, etc. it will corrupt the project file, resulting in a complete loss of all your hard work. I strongly recommend Final Cut Express, the interface isn't as familiar as iMovie but it gets the job done every time.

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